Conductive thin film for semiconductor device, semiconductor device, and method of manufacturing the same

ABSTRACT

A semiconductor device  1  obtained by depositing, on a substrate  2 , a gate electrode  4  formed by a conductive thin film containing Mo atoms and Ag atoms, a gate insulating film  6 , an α-Si:H(i) film  8 , a channel protection layer  10 , an α-Si:H(n) film  12 , a source/drain electrode  14  formed by a conductive thin film containing Mo atoms and Ag atoms, a source/drain insulating film  16 , and a drive electrode  18 . By using a conductive thin film containing Mo atoms and Ag atoms, the gate electrode  4  and the source/drain electrode  14  are formed to manufacture the semiconductor device  1 . Thus, the conductive thin film for a semiconductor device, having high adhesion strength to a substrate, an insulating layer, and the like, a semiconductor device which operates stably without deteriorating the performance, and a method of efficiently manufacturing the conductive thin film and the semiconductor device can be provided.

This Application is a 371 of PCT/JP02/04556 May 10, 2002.

TECHNICAL FIELD

The present invention relates to a conductive thin film for asemiconductor device such as a semiconductor transistor, a semiconductordevice, and a method of manufacturing the same.

BACKGROUND ART

A TFT is a very important component as a main component of a display ofa portable personal computer, a laptop personal computer, a television,or the like.

Companies manufacture TFTs by their methods. Since the process ofmanufacturing a TFT is complicated and various metals and metal oxidesare deposited a plurality of times, simplification of the process isdemanded.

In a process of manufacturing a conventional TFT array, as materials ofa gate electrode and a source/drain electrode, metals such as Cr and TaWare used.

Although Cr is easily processed, there is a problem that Cr is easilycorroded. Although TaW is resistive to corrosion and the like, it has aproblem of high electric resistance and the like.

Consequently, a TFT array using wires made mainly of aluminum as a metalwhich is easily processed and has low electric resistance has beenproposed.

However, when an aluminum electrode is in direct contact with a siliconlayer and a drive electrode, problems occur such that aluminum isdiffused into the silicon layer, thereby deteriorating deviceperformance, and aluminum is oxidized and converted into alumina, itincreases the electric resistance with the drive electrode, and thedevice does not operate normally.

Attempt is being made to reduce the contact resistance with the driveelectrode by sandwiching the aluminum electrode by Mo or Ti.

In order to sandwich the aluminum electrode, however, a film made of Moor Ti has to be formed first, after that, a film of a metal containingaluminum as a main component is formed, and a film made of Mo or Ti hasto be formed again. Consequently, there is a drawback that the processis complicated.

On the other hand, attempt is also being made to solve the problem byusing a silver or copper electrode. However, silver and copper have lowadhesion to with a silicon nitride film, a silicon wafer, or the likewhich is made of glass or an insulating film. It causes a problem suchthat silver and copper come off during the manufacturing process.

An object of the invention is to provide a conductive thin film for asemiconductor device having strong adhesion to a substrate, aninsulating layer, or the like, a semiconductor device that stablyoperates without deteriorating performance, and a method of efficientlymanufacturing the film and the device.

The inventors herein have studied wholeheartedly and, as a result, foundthat the object can be achieved by using a conductive thin filmcontaining Ag atoms and Mo atoms for a gate electrode and/or asource/drain electrode of a semiconductor device.

DISCLOSURE OF INVENTION

According to the present invention, a conductive thin film containing Agatoms and Mo atoms, having strong adhesion to a substrate, an insulatinglayer, and the like, and particularly preferably used for asemiconductor device is provided.

A semiconductor device in which at least one of a gate electrode and asource/drain electrode is made by the conductive thin film is provided.

By forming a gate electrode and/or a source/drain electrode from theconductive thin film, even when an electrode wire is in direct contactwith a silicon layer, diffusion of metal atoms into the silicon layercan be prevented, so that the performance of a semiconductor deviceobtained does not deteriorate.

Further, even when a drive electrode is formed directly on the electrodewire, contact resistance can be prevented from being increased. Thus, asemiconductor device which operates stably can be obtained.

Particularly, an example of the semiconductor device is a semiconductortransistor including a field effect transistor such as a TFT. In anexample of a concrete structure, a gate electrode, a semiconductorlayer, a source/drain electrode, and a drive electrode are disposed on asubstrate.

In a conductive thin film for a semiconductor device (conductive thinfilm) according to the invention, preferably, the film contains 0.5 to70% by weight of Mo atoms.

Further, more preferably, the conductive thin film of the inventioncontains 30 to 99.5% by weight of Ag atoms and 0.5 to 70% by weight ofMo atoms. Further more preferably, the conductive thin film contains 70to 99% by weight of Ag atoms and 1 to 30% by weight of Mo atoms. Furthermore preferably, the conductive thin film contains 85 to 98% by weightof Ag atoms and 2 to 15% by weight of Mo atoms.

By setting the Ag atoms and Mo atoms within the ranges, the adhesionbetween the conductive thin film and a substrate or an insulating layercan be largely increased. Consequently, the conductive thin film can bepreferably applied to a semiconductor device.

In the case of using the conductive thin film of the invention for asemiconductor device, at least one of the gate electrode and thesource/drain electrode is formed by the conductive thin film containingAg atoms and Mo atoms at any of the rates.

In the conductive thin film of the invention, preferably, resistivity is5 μΩ·cm or less.

Further, in a semiconductor device of the invention, preferably, atleast one of the gate electrode and the source/drain electrode is formedby the conductive thin film containing Ag atoms and Mo atoms and havingresistivity of 5 μΩ·cm or less.

By setting the resistivity to be within the range, delay of a signal fordriving a liquid crystal or the like can be effectively prevented.

In the conductive thin film of the invention, preferably, the Mo atomsare Mo atoms derived from an Mo/Al compound, an Mo/Be compound, an Mo/Gacompound, an Mo/Ge compound, an Mo/Ir compound, an Mo/Pt compound, anMo/Re compound, an Mo/Si compound, an MoW alloy, an MoTa alloy, or anMoRh alloy.

When the Mo atoms are derived from any of such materials, dispersibilityof the Mo atoms is improved and stability of the conductive thin filmcan be improved.

Another aspect of the present invention relates to a method ofmanufacturing a conductive thin film, wherein the conductive thin filmis formed by sputtering. In the method, it is preferable to use asputtering target containing Ag atoms and Mo atoms. Further anotheraspect of the invention relates to a method of manufacturing asemiconductor device, for forming at least one of a gate electrode and asource/drain electrode by a conductive thin film formed by using themethod of manufacturing the conductive thin film.

By forming a film by sputtering, a process of depositing Mo/Al/Mo,Ti/Al/Ti or the like can be simplified and a semiconductor device can bemanufactured efficiently.

By using a sputtering target mainly made of Ag to which an Mo compoundsuch as an Mo/Al compound, an Mo/Be compound, an Mo/Ga compound, anMo/Ge compound, an Mo/Ir compound, an Mo/Pt compound, an Mo/Re compound,an Mo/Si compound, an MoW alloy, an MoTa alloy, or an MoRh alloy isadded, dispersibility of Mo is improved and a film can be stably formedby sputtering.

According to the method, adhesiveness of the gate electrode and thesource/drain electrode to a substrate (for example, glass substrate) anda silicon layer (such as silicon nitride film, semiconductor layer, orsilicon wafer) is high and peeling does not occur during a manufacturingprocess. Thus, a semiconductor can be manufactured stably.

Further, it is preferable to use a sputtering target obtained byreducing, rolling, and sintering a mixture made of one or more kinds ofoxides selected from oxides of Al, Be, Ga, In, Ge, Ir, Pt, Re, Si, W,Ta, and Rh, an Ag oxide, and an Mo oxide.

By using such a sputtering target, a film can be formed stably at thetime of sputtering.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a cross sectional view showing an embodiment of asemiconductor device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A conductive thin film, a semiconductor device, and a method ofmanufacturing the same will be described hereinbelow.

1. Conductive Thin Film

(1) Kinds

A conductive thin film of the invention contains Ag atoms and Mo atoms.For example, a single Ag as an Ag atom source is used as a maincomponent and an Mo atom is added to the Ag atom.

A Mo atom source is not particularly limited. Mo atoms may be added assingle Mo atoms or as a alloy compounds a metal mixture, or a metalcompound.

Examples are Mo/Al compounds, Mo/Be compounds, Mo/Ga compounds, Mo/Gecompounds, Mo/Ir compounds, Mo/Pt compounds, Mo/Re compounds, Mo/Sicompounds, MoW alloys, MoTa alloys, MoRe alloys, and the like.

Examples of the Mo/Al compounds are MoAl₁₂, MoAl₅, Mo₃Al₈, and Mo₃Al.Examples of the Mo/Be compounds are MoBe₁₂, MoBe₂₂, Mo₃Be, and MoBe₂.Examples of the Mo/Ga compounds are Mo₃Ga and Mo₆Ga₃₁. Examples of Mo/Gecompounds are MoGe₂, Mo₂Ge₃, Mo₃Ge, and Mo₃Ge₂. Examples of the Mo/Ircompounds are MoIr and MoIr₃. An example of Mo/Pt compound is MoPt₃. Anexample of the Mo/Re compound is MoRe. Examples of the Mo/Si compoundsare MoSi₂, Mo₃Si, and Mo₅Si₃.

As a third component, another metal atoms may be added together with theMo atoms to the Ag atoms.

The kind of the third component is not particularly limited as long asit is a metal which is not diffused into the silicon layer or a metalwhich does not exert an influence on the performance of a semiconductordevice when it is diffused. Examples of such a component are Pd, W, Cu,and Au.

The addition amount of the third component is not particularly limitedas long as it is in a range where no influence is exerted on theconductivity of the conductive thin film and the performance of thesemiconductor device.

(2) Ratio

In the case of using the conductive thin film for an electrode,preferably, 0.5 to 70% by weight of Mo atoms is contained for thefollowing reasons. When the content of Mo becomes lower than 0.5% byweight, an effect of adding Mo may not be displayed. On the other hand,when the content of Mo exceeds 70% by weight, there is a case that theresistance value of the gate electrode and that of the source/drainelectrode increase or there is a case that abnormal discharge duringsputtering increases.

For such reasons, it is most preferable to set the content of Mo atomsin a conductive thin film to 2 to 15% by weight.

(3) Resistivity

The resistivity of the conductive thin film is preferably 5 μΩ·cm orless. The reason is that when the resistivity exceeds 5 μΩ·cm, delay ina signal for driving a liquid-crystal or the like may occur.

For such a reason, it is more preferable to set the resistivity of theconductive thin film to 3 μΩ·cm less.

2. Method of Manufacturing Conductive Thin Film

A conductive thin film of the invention is formed by sputtering.

In this case, a sputtering method and a sputtering system are notparticularly limited. Examples of the sputtering method arehigh-frequency sputtering, DC sputtering, RF sputtering, DC magnetronsputtering, RF magnetron sputtering, ECR plasma sputtering, and ion beamsputtering.

A sputtering target is not particularly limited as long as it is atarget for forming a conductive thin film satisfying a targetperformance. Sputtering targets suitably used are, for example, asputtering target obtained by reducing, rolling, and sintering a mixtureof an Ag oxide and an Mo oxide, a sputtering target obtained byreducing, rolling, and sintering a mixture of one or more kinds ofoxides selected from the group of Al, Be, Ga, In, Ge, Ir, Pt, Re, Si, W,Ta, and Rh, Ag oxide, and Mo oxide, a sputtering target obtained byinserting a plate made of Mo singly or an Mo alloy into an Ag target apart of which is cut and removed, and a sputtering target obtained byinserting a plate made of Ag singly into a target of single Mo or an Moalloy a part of which is cut and removed. By using such a sputteringtarget, a film can be stably formed at the time of sputtering.

3. Semiconductor Device

The semiconductor device of the invention has a gate electrode and asource/drain electrode formed by the conductive thin film. Theconstitution (substrate, silicon layer, drive electrode, and the like)other than the gate electrode and/or the source/drain electrode is notparticularly limited but can be made of normal materials.

In the invention, at least one of the gate electrode and thesource/drain electrode may be formed by the conductive thin film. Inthis case, as a material of an electrode which is not formed by theconductive thin film, a normal material can be used. Further, in thecase where wiring is necessary, from the viewpoint of the constitutionof the semiconductor device, a conductive thin film may be used aswiring.

4. Method of Manufacturing Semiconductor Device

In the method of manufacturing the semiconductor device of theinvention, at least one of the gate electrode and the source/drainelectrode is formed from the conductive thin film formed by using themethod of manufacturing the conductive thin film.

In this case, means for patterning the conductive thin film formed bysputtering into a target electrode shape is not particularly limited butmay be performed by using photoetching or the like.

Further, in the semiconductor device of the invention, the method ofmanufacturing components other than the electrodes is not limited butmay be a normal method using a normal material.

EXAMPLES

The invention will be described in more detail hereinbelow on the basisof examples. However, the invention is not limited to the examples.

Example 1

A sputtering target obtained by opening a hole of 10 mmφ in an Ag targetof 1.4 inches φ and inserting an Mo target of 10 mmφ into the hole wasused and a thin film having a film thickness of 2,000 Å was formed on asilicon wafer by DC magnetron sputtering at a substrate temperature of300° C. The content of Mo in the thin film was 5.1% by weight andresistivity was 2.4 μΩ·cm. Adhesion strength by a scratch test of thethin film was 5.57N. The scratch test was conducted as follows.

(1) Measurement Principle

A coated substrate is scratched with a diamond cone at constant speedwhile increasing a load at constant speed, and a destruction whichoccurs in or on the thin film is detected by an AE sensor. By using aload at which an AE signal rapidly goes high as a critical load, aquantitative value of adhesion strength is obtained.

By observing the surface after the scratch, a load of destruction(interface peel, film base material destruction, and the like) in apredetermined aspect is calculated.

In measurement of this time, as a result of surface observation afterscratch, the substrate was exposed at the critical load value or less.Consequently, adhesion strength was calculated by the latter method.

(2) Apparatus and Measurement Conditions

-   scratch tester: Micro-Scratch-Tester manufactured by CSEM-   scratch distance: 10.0 mm-   scratch load: 0 to 10.0N-   load rate: 10.0 N/min-   scratch speed 10.0 mm/min-   diamond cone shape: tip R: 200 μm (120°)    (3) Calculation of Adhesion Strength

A sample of each scratch test was observed by a light microscope. Apoint where a silicon wafer as a substrate is exposed was used as a peelpoint of the film and the distance from the scratch start point wasmeasured, thereby calculating a peel load. The results are shown inTable 1.

Examples 2 to 4

Thin films were formed in a manner similar to Example 1 except that thecontent of Mo and the content of the third metal in the sputteringtarget were changed as shown in Table 1, and evaluation was made. Theresults are shown in Table 1.

Comparative Example 1

A thin film was formed in a manner similar to Example 1 except that theMo target was not used but only the Ag target was used, and evaluationwas made. The result is shown in Table 1.

TABLE 1 The third Adhesion Mo content metal content Resistivity strength(wt %) (wt %) (μΩ · cm) (N) Example 1 5.1 — 2.4 5.57 Example 2 2.1 0.5(Cu) 2.3 5.71 Example 3 2.6 1.0 (In) 2.7 5.84 Example 4 2.5 0.6 (Ga) 3.85.12 Comparative 0 — 2.1 0.40 example 1

Example 5

An embodiment of the invention will be described by using FIG. 1.

FIG. 1 is a cross sectional view showing an embodiment of asemiconductor device of the invention.

On a light transmittable glass substrate 2, a metal Ag (resistivity: 2.4μΩ·cm) containing 5% by weight of Mo was deposited to a film thicknessof 2,500 Å by high frequency sputtering. The layer was subjected tophotoetching using a nitric acid-acetic acid-phosphoric acid solution asan etchant, thereby forming a gate electrode 4 (gate electrode wire) ofa desired shape.

Next, a gate insulating film 6 as a first silicon nitride (SiNx) film(silicon layer) was deposited to a film thickness of 3,000 Å.

Subsequently, a SiH₄—N₂ mixed gas was used as a discharge gas and anα-Si:H(i) film (silicon layer) 8 was deposited to a film thickness of3,500 Å.

Further, on the α-Si:H(i) film 8, by using an SiH₄—NH₃—N₂ mixed gas as adischarge gas, a second silicon nitride (SiNx) film was deposited to afilm thickness of 3,500 Å. From the second SiNx film, a desired channelprotective layer (silicon layer) 10 was formed by dry etching using aCF₄ gas.

Subsequently, an α-Si:H(n) film (silicon layer) 12 was deposited to afilm thickness of 3,000 Å by using an SiH₄—H₂—PH₃ mixed gas.

The gate insulating film 6, α-Si:H(i) film (silicon layer) 8, channelprotection layer (silicon layer) 10, and α-Si:H(n) film (silicon layer)12 were deposited by glow discharge CVD.

After that, Ag (resistivity: 3.6 μΩ·cm) containing 2% by weight of MoPt₃was deposited to a film thickness of 0.3 μm by sputtering. This layerwas subjected to photoetching using a nitric acid-acetic acid-phosphoricacid solution as an etchant, thereby patterning a desired source/drainelectrode 14.

Further, by performing both dry etching using a CF₄ gas and wet etchingusing a hydrazine (NH₂NH₂.H₂O) solution on the α-Si:H film, the patternof the α-Si:H(i) film 8 and the pattern of the α-Si:H(n) film 12 wereformed as desired patterns.

On the desired patterns, a source/drain insulating film (silicon layer)16 as a third silicon nitride (SiNx) film was deposited to a filmthickness of 3,000 Å by glow discharge CVD. At this time, a SiH₄—NH₃—N₂mixed gas was used as a discharge gas to form the third SiNx film.

Further, by photoetching using the dry etching with the CF₄ gas, adesired through hole was formed as an output port of the gate electrode4, an output port of the source electrode 14, and an electric contactpoint between the drain electrode 14 and a pixel electrode (driveelectrode) 18.

After that, by making argon plasma act on the surface of the metal Agelectrode, the surface was cleaned. An amorphous transparent conductivefilm made of indium oxide and zinc oxide as main components wasdeposited by sputtering. As a target, an In₂O₃—ZnO sintered body inwhich the atom ratio [In/(In+Zn)] between In and Zn was adjusted to 0.83and which is disposed in a planar magnetron cathode was used. By using,as a discharge gas, an argon gas obtained by mixing pure argon or anoxygen gas of a small amount of about 1% by volume, a transparentelectrode film was deposited to a film thickness of 1,200 Å.

When the In₂O₃—ZnO film was analyzed by the X-ray diffraction method, nopeak was observed and the film was amorphous. The film was patternedinto the desired pixel electrode 18 and a lead electrode by photoetchingusing a solution of 3.4% by weight of oxalic acid and, further, a lightshielding film pattern was formed, thereby completing an α-SiTFTsubstrate.

A TFT-LCD flat-panel display was manufactured by using the substrate.After that, when a video signal was input and display performance waschecked, the display performance was excellent.

Comparative Example 2

Comparative Example 2 was carried out in a manner similar to Example 5except that metal Al (resistivity: 7 μΩ·cm) containing 2% by weight ofNd was used for the Ag/Mo and Ag/Mo/Pt wires in Example 5. In thedisplay performances of the case, color developed spots were generatedin the vertical and lateral directions and it was recognized that asignal was not input normally.

Industrial Applicability

According to the invention, a conductive thin film for a semiconductordevice having high adhesion strength to a base material, an insulatinglayer, and the like, the semiconductor device which operates stablywithout deteriorating performance, and the method of efficientlymanufacturing the same can be provided.

1. A conductive thin film for a semiconductor device, containing Agatoms and 1 to 30% by weight of Mo atoms.
 2. The conductive thin filmfor a semiconductor device according to claim 1, which is a filmcomprising Mo atoms and Ag atoms and optionally any of Cu atoms, Inatoms, and Ga atoms.
 3. The conductive thin film for a semiconductordevice according to claim 1, wherein a resistivity of the conductivethin film is 5 μΩ·cm or less.
 4. The conductive thin film for asemiconductor device according to claim 1, wherein the Mo atoms are Moatoms derived from an Mo/Al compound, an Mo/Be compound, an Mo/Gacompound, an Mo/Ge compound, an Mo/Ir compound, an Mo/Pt compound, anMo/Re compound, an Mo/Si compound, an MoW alloy, an MoTa alloy, or anMoRh alloy.
 5. A method of manufacturing the conductive thin film for asemiconductor device according to claim 1, comprising forming theconductive thin film by sputtering.
 6. The method of manufacturing theconductive thin film for a semiconductor device according to claim 5,wherein a sputtering target obtained by reducing, rolling, and sinteringa mixture made of an Ag oxide and an Mo oxide is used.
 7. The method ofmanufacturing a conductive thin film for a semiconductor deviceaccording to claim 5, wherein a sputtering target obtained by reducing,rolling, and sintering a mixture made of one or more kinds of oxidesselected from oxides of Al, Be, In, Ga, Ge, Ir, Pt, Re, Si, W, Ta, andRh, an Ag oxide, and an Mo oxide is used.
 8. A semiconductor devicecomprising a gate electrode and a source/drain electrode, wherein atleast one of the gate electrode and the source/drain electrode is formedof a semiconductor device conductive thin film containing Ag atoms and 1to 30 wt. by weight of Mo atoms.
 9. A method of manufacturing thesemiconductor device according to claim 8, comprising forming at leastone of a gate electrode and a source/drain electrode by a conductivethin film formed by using the method of manufacturing a conductive thinfilm for a semiconductor device according to claim
 3. 10. The conductivethin film for a semiconductor device according to claim 3, wherein theresistivity of the conductive thin film is 3 μΩ·cm or less.
 11. Theconductive thin film for a semiconductor device according to claim 1,wherein the Mo atoms are present in an amount of 2 to 15% by weight.